1. Field of the Invention
This invention relates to a print head device for use in combination with an ink cartridge mounted therein, and an ink jet printer incorporating the print head device, and the ink cartridge.
2. Prior Art
Ink jet printers have the inconvenience that an ink meniscus at nozzle tips of a print head thereof is destroyed even by a slight shock or impact (for instance, one caused by a fall of the ink jet printer from a position one or two centimeters high). The destruction of meniscus causes xe2x80x9cthinned nozzlesxe2x80x9d which means a faulty ink-discharging action of nozzles or xe2x80x9cangled jetsxe2x80x9d which means undesirably angled jets of ink drops, resulting in a faulty printing operation. Especially, in the case of ink jet printers of a type which has ink delivery ports of an ink cartridge connected to connecting caps of a head unit thereof in surface-to-surface contact, more particularly, a type which has seal packings interposed between the connecting caps and the ink delivery ports, respectively, the seal packings are contracted and expanded by a shock to cause pressure fluctuations within closed spaces inside the seal packings. The pressure fluctuations can propagate to ink, resulting in destruction of the ink meniscus at nozzle tips.
Users of ink jet printers which are generally commercially available are advised to carry out cleaning of a print head of their printer by manually instructing the cleaning operation thereto even when it is simply moved e.g. for a change of position where it is placed, since there is a fear that the ink meniscus at nozzle tips thereof is destroyed.
Therefore, in the case of ink jet printers of a portable type or ones which have to be frequently carried from one place to another, automatic or manual cleaning of a print head thereof is very frequently required. Such ink jet printers wastefully consume a large amount of ink, which degrades commercial value thereof.
It is an object of the invention to provide a print head device, an ink jet printer incorporating the print head device, and an ink cartridge, which are capable of preventing an ink meniscus at nozzle tips of the print head device from being destroyed by a shock or impact applied to the ink jet printer.
To attain the above object, according to a first aspect of the invention, there is provided a print head device in which an ink cartridge storing ink therein and having an ink delivery port for delivering the ink therefrom is removably mounted for use therewith, the print head device comprising:
a seal packing arranged such that the seal packing is brought into airtight contact with the ink cartridge when the ink cartridge is mounted in the print head device, such that the seal packing encloses the ink delivery port, thereby defining an inner space within the seal packing, for airtight communication between the ink delivery port and the inner space; and
pressure fluctuation-accommodating means for accommodating pressure fluctuations within the ink delivery port and the inner space in communication with each other.
According to this print head device, when the print head device having the ink cartridge mounted therein receives a shock or impact, inertia of the ink cartridge causes expansion and contraction or compression of the seal packing, whereby the volume of the inner space inside the seal packing is fluctuated, causing pressure fluctuations within the ink delivery port and the inner space in communication with each other. However, the pressure fluctuations are accommodated by the pressure fluctuation-accommodating means. This prevents the pressure fluctuations from propagating to ink, and thereby inhibits pulsation of the ink. Thus, the print head device according to the first aspect of the invention can suitably accommodate pressure fluctuations within the ink delivery port and the inner space in communication with each other, thereby effectively preventing destruction of an ink meniscus at tips of ink nozzles. This enhances shock resistance of the print head device.
Preferably, the pressure fluctuation-accommodating means comprises an air communication passage, the air communication passage having one end open to the inner space within the seal packing and another end open to the atmosphere.
According to this preferred embodiment, the pressure fluctuations within the ink delivery port and the inner space in communication with each other are accommodated by air flows in the air communication passage.
More preferably, the print head device includes a cartridge-receiving portion for receiving the ink cartridge thereat, and the air communication passage comprises a groove formed in a surface of the cartridge-receiving portion, and a film hermetically covering the groove except for opposite ends thereof.
According to this preferred embodiment, the air communication passages can be easily formed by forming a groove in advance in the surface of the cartridge-receiving portion, and affixing a film over the groove by thermocompression bonding. Further, the air communication passages formed do not produce unacceptably concave or convex portions on the surface of the cartridge-receiving portion.
Preferably, the air communication passage extends in a meandering manner.
According to this preferred embodiment, it is possible to minimize evaporation of a solvent, such as water or the like, contained in ink.
More preferably, a drop of non-volatile sealing liquid is sealingly held in the air communication passage, for motion in accordance with air flows in the air communication passage.
According to this preferred embodiment, it is possible to prevent evaporation of a solvent contained in ink. The provision of non-volatile sealing liquid in the air communication passage is useful especially when an ink diluted by a highly volatile solvent is employed.
Alternatively, the pressure fluctuation-accommodating means comprises a pouch formed of a flexible membrane arranged in an outer space outside the seal packing, the outer space being in communication with the atmosphere, and a communication passage permitting airtight communication between the pouch and the inner space.
According to this preferred embodiment, when the print head device having the ink cartridge mounted therein receives a shock to cause expansion and contraction or compression of the seal packing, pressure in the inner space inside the seal packing is fluctuated. However, the pressure fluctuations are accommodated by air flows to and from the pouch which is formed of a flexible membrane and in communication with the inner space via the communication passage. This prevents fluctuations in the volume of the inner space inside the seal packing from developing a large pulsation of ink supplied from the ink delivery port to the ink nozzles of the print head device. Further, it is possible to positively prevent evaporation of a solvent, such as water or the like, contained in ink.
Preferably, the communication passage extends through the seal packing.
Alternatively, the ink cartridge further includes a casing, an absorbent filled in the casing, for absorbing the ink for storage, and a filter arranged between the absorbent and the ink delivery port;
the print head device further comprising a connecting portion for being inserted into the ink delivery port when the ink cartridge is mounted in the print head device such that the connecting portion pushes the filter inward, for permitting the ink delivered from the ink delivery port to flow therethrough;
the seal packing comprising a wall forming a generally hollow cylindrical shape and constructed such that the wall is bent inward when an external force is applied to the seal packing in a compressing direction, whereby the seal packing doubles as the pressure fluctuation-accommodating means.
According to this preferred embodiment, when the print head device having the ink cartridge mounted therein receives a shock to cause relative motion of the ink cartridge toward the print head device, the connecting portion of the print head device pushes inward the filter of the ink cartridge by a distance of the motion, and at the same time the seal packing is contracted. In this process, the seal packing is bent inward to reduce the volume of the inner space, whereby a positive pressure is generated in the inner space, while the volume of evacuated space which is produced by the insertion of the connecting portion of the print head device and in communication with the ink delivery port is increased whereby a negative pressure is generated in the evacuated space. This causes air to flow from the inner space inside the seal packing to the evacuated space to accommodate changes in pressure generated in the inner space and the evacuated space such that the positive and negative pressures cancel each other. Inversely, when the ink cartridge is moved away from the print head device, the motion acts to permit the filter to push out the connecting portion by a distance of the motion, and at the same time the seal packing to be extended. Extension of the seal packing increases the volume of the inner space to generate a negative pressure within the inner space, while the volume of the evacuated space is reduced to generate a positive pressure therein. This causes air to flow from the evacuated space to the inner space inside the seal packing to accommodate changes in pressure such that the negative and positive pressures cancel each other. It should be noted that the cross-sectional shape of the wall forming the generally hollow cylindrical shape is not limited to a circular arc, but the wall may have any cross-sectional shape, such as a segment of ellipse, so long as it is bent arcuately inward. As described above, according to the preferred embodiment, changes in pressure or pressure fluctuations in the inner space and the evacuated space can be accommodated such that they cancel each other. Hence, it is possible to effectively prevent destruction of an ink meniscus at the nozzle tips, thereby enhancing shock resistance of the print head device by the above-described construction, which is simple.
Preferably, the seal packing is generally slightly bent inward when the seal packing is in a free state.
According to this preferred embodiment, the seal packing can be naturally bent inward when the external force is applied thereto in the compressing direction.
Preferably, the seal packing has an inner diameter substantially equal to an outer diameter of the filter.
According to this preferred embodiment, the amount of a change in volume of the inner space inside the seal packing caused by the relative motion of the ink cartridge toward or away from the print head device is substantially equal to that in the evacuated space simultaneously caused by the relative motion, so that it is possible to minimize the change in the internal pressure inside the seal packing and the ink cartridge.
To attain the above object, according to a second aspect of the invention, there is provided an ink cartridge which stores ink therein, and is removably mounted in a print head device for use therewith, the print head device having a seal packing arranged such that the seal packing is brought into airtight contact with the ink cartridge to define an inner space within the seal packing when the ink cartridge is mounted in the print head device, the ink cartridge comprising:
a cartridge casing for being brought into airtight contact with the seal packing;
an ink delivery port formed through the cartridge casing, for delivering the ink therefrom, the ink delivery port being arranged such that the ink delivery port establishes airtight communication with the inner space defined within the seal packing when the ink cartridge is mounted in the print head device; and
pressure fluctuation-accommodating means for accommodating pressure fluctuations within the ink delivery port and the inner space in communication with each other.
According to this ink cartridge, when the print head device having the ink cartridge mounted therein receives a shock or impact, inertia of the ink cartridge causes expansion and contraction or compression of the seal packing, whereby the volume of the inner space inside the seal packing is fluctuated, causing pressure fluctuations within the ink delivery port and the inner space in communication with each other. However, the pressure fluctuations are accommodated by the pressure fluctuation-accommodating means. This prevents the pressure fluctuations from propagating to ink, and thereby inhibits pulsation of the ink. Thus, the ink cartridge according to the second aspect of the invention can suitably accommodate pressure fluctuations within the ink delivery port and the inner space in communication with each other, thereby effectively preventing destruction of an ink meniscus at tips of ink nozzles. This enhances shock resistance of the ink cartridge.
Preferably, the pressure fluctuation-accommodating means comprises an air communication passage formed in a surface of the cartridge casing, the air communication passage having one end open to the inner space within the seal packing and another end open to the atmosphere.
According to this preferred embodiment, the pressure fluctuations within the ink delivery port and the inner space in communication with each other are accommodated by air flows in the air communication passage.
More preferably, the air communication passage comprises a groove formed in the surface of the cartridge casing, and a film hermetically covering the groove except for opposite ends thereof.
According to this preferred embodiment, the air communication passages can be easily formed by forming a groove in advance in the surface of the cartridge casing, and affixing a film over the groove by thermocompression bonding. Further, the air communication passages formed do not produce unacceptably concave or convex portions on the surface of the cartridge casing where the sealing packing is brought into airtight contact.
Preferably, the air communication passage extends in a meandering manner.
According to this preferred embodiment, it is possible to minimize evaporation of a solvent, such as water or the like, contained in ink.
Preferably, a drop of non-volatile sealing liquid is sealingly held in the air communication passage, for motion in accordance with air flows in the air communication passage.
According to this preferred embodiment, it is possible to prevent evaporation of a solvent contained in ink. The provision of non-volatile sealing liquid in the air communication passage is useful especially when an ink diluted by a highly volatile solvent is employed.
Alternatively, the print head device further includes a connecting portion for being inserted into the ink delivery port when the ink cartridge is mounted in the print head device, for permitting the ink delivered from the ink delivery port to flow therethrough;
the ink cartridge further comprising an absorbent filled in the cartridge casing, for absorbing the ink for storage, and a filter arranged between the absorbent and the ink delivery port, for being pushed inward when the ink cartridge is mounted in the print head device;
the cartridge casing having a delivery port rim portion defining the ink delivery port therein and being brought into airtight contact with the seal packing, the delivery port rim portion being formed with a filter-receiving portion for receiving the filter therein; and
the pressure fluctuation-accommodating means comprises an air communication passage formed through the delivery port rim portion, for communication between an inside of the filter-receiving portion and an outer space outside the seal packing, and valve means arranged for the air communication passage for opening inward and outward according to the pressure fluctuations.
According to this ink cartridge, when the print head device having the ink cartridge mounted therein receives a shock to cause relative motion of the ink cartridge toward and away from the print head device, the seal packing is compressed and expanded. If the compression or expansion of the seal packing generates a positive pressure within the inner space and an evacuated space which is produced by the insertion of the connecting portion of the print head device and in communication with the ink delivery port, the valve means opens outward to permit air to flow out via the air communication passage, while if a negative pressure is generated in the same, the valve means opens inward to permit air to flow in via the air communication passage. As a result, the changes in pressure or pressure fluctuations within the inner space and the evacuated space caused by changes in volume of these spaces are accommodated by air flows through the air communication passage opened and closed by the valve means.
More preferably, the air communication passage includes a first passage, and a second passage, the valve means including a positive pressure valve element arranged for the first passage, for opening outward when a positive pressure is generated within the ink delivery port and the inner space in communication with each other, and a negative pressure valve element arranged for the second passage, for opening inward when a negative pressure is generated within the ink delivery port and the inner space in communication with each other.
According to this preferred embodiment, the valve means and a valve sheet brought into intimate contact with the valve means can be configured to have a simple construction such that the valve means is accurately opened and closed.
To attain the above object, according to a third aspect of the invention, there is provided an ink jet printer for use in combination with an ink cartridge storing ink and having an ink delivery port for delivering ink therefrom, the ink jet printer comprising the print head device according to the first aspect of the invention described above.
This ink jet printer is advantageous in that it is excellent in shock-resistance and suitable for a portable use.
The above and other objects, features, and advantages of the invention will become more apparent from the following detailed description taken in conjunction with the accompanying drawings.